My place is in NY State, but a quick search found that you should present a filled out
REV-1220 PA Exemption Certificate
The info
here states: Using the REV-1220, exemptions from tax can be claimed because: ...the property or service is being directly used in manufacturing, mining, dairying, processing,
farming and/or shipbuilding;...
Here is another PDF (page 5) that cover the
need for a tax exempt number: TAX EXEMPTION CERTIFICATES When purchasing items of tangible personal property or services that are considered to be tax exempt, the farmer must complete a PA Exemption Certificate (
REV-1220) for the supplier.
Farmers are not required to obtain a Sales Tax license number or submit a Sales Tax license number to a supplier prior to receiving a Sales Tax exemption on purchases of exempt tangible personal property directly used in farming operations. One exemption certificate may cover several purchases.
Note that
vendors are not required to accept the 1220 form: The vendor is not required to accept the Exemption Form. In the event a qualified business is denied exemption from Sales and Use Tax,
the business will be required to pay the tax and petition for refund with the Board of Appeals.
I suggest prepare a stack of the forms partially filled out with your information typed in and check the applicable boxes when purchasing and present the form at the store.